An area sensitive x-ray detector is to be harnessed to x-ray crystallographic data collection for a variety of high resolution structure analyses. The new instrument is to augment the UCSF structural capability which is currently vastly oversubscribed. At present persons typically wait in turn for one month to six weeks for time on one of the existing area detectors. The new instrument requested is to overcome this rate limiting step in the structural science that is being accomplished. In addition, newer technology has been developed which makes data collection more efficient and accurate with the requested instrumentation. As structural analysis moves to the area where it can now ask scientific questions using many mutations, or using modified inhibitors aimed at designing improved therapeutics, study of a single protein system can efficiently occupy 50% of the time on one data collection instrument. It is now clear that understanding of the properties of altered proteins or altered inhibitory compounds will require an analysis of structure as thoroughly as for the native proteins. The speed with which the directed mutagenesis is accomplished requires rapid structural analysis for the structuralist to remain close to the scientific questions of importance. The instrument will support an immediate user group of four core crystallographic research groups, along with collaborations which include eight other research teams that collaborate directly with these core groups. The instrument will be maintained and investigators trained by Melvin Jones, a crystallographer (M.S. Caltec in crystallography) and long time associate of the UCSF structure groups. An advisory committee includes structural biologist Dr. John W. Sedat along with core users to ensure equitable distribution.